The U.S. Army Corps of Engineers is constructing a 2,700-foot-long concrete dam across the lower Ohio River called the Olmsted Lock and Dam project, located near Olmsted, Ill. at Ohio River Mile 964.4. Once completed, the new system will replace two existing dams located upstream and downstream of the dam. The Olmsted Dam will enable tows to pass through this busy stretch of river in one hour rather than five. The dam will consist of five Tainter gates and barge-operated wicket gates that can be raised or lowered for navigational purposes. Approximately 60% of the year, during high water, tows will bypass the locks and go over the top of the wicket gate portion of the dam. The project consists of two 110′×1,200′ locks and a dam comprised of 5 Tainter gates, 1,400′ of barge-operated wickets and a fixed weir.
The dam is being constructed “in-the-wet,” or underwater, rather than in dry cofferdams. Precast segments (or shells) are constructed on land and moved into the river where they are placed in their final location underwater. A concrete batch plant set-up adjacent to the river provides the required concrete material to construct the shells. Each shell is constructed in a Precast Yard. This yard will produce 47 concrete shells, the largest of which will weigh in excess of 4,200 tons. Each of the shells which are approximately 102′ wide, 125′ long, and 35′ tall will be moved and lifted by a 5340-ton capacity super-gantry crane. The gantry crane is power-driven on train rails and moves each of the shells slowly to a cradle. When the gantry crane has positioned the shell over the cradle, it then lowers the shells on to the cradle. The cradle then lowers the shells down a long skid-way to the river's edge, partially submerging the shell. After the shell is partially submerged on the cradle, a gantry crane catamaran barge in the river picks the shell off the cradle and transports the shell to a location in the river where the shell will be lowered to the river bottom. Once the shell is lowered into place, the underside of each shell is pumped full of Tremie Concrete. The Tremie Concrete has the capability of solidifying underwater, providing a foundation between the shell and the prepared riverbed. The entire process of building and placing shells won't be completed until the dam stretches across the river from one side to the other side.
Dams may be built in close proximity to seismic fault lines and require a seismic design safety factor. Due to the possibility of seismic activity, the seams between the shells are designed to allow for a small amount of movement.
Products such as Bondaflex sponge rubber expansion joint filler, available from Monmouth R4ubber and Plastics Co., Long Branch, N.J., have been used before to fill gaps between dam sections, providing a level of movement between each of the shells. Bondaflex has the useful feature of compressing slightly under pressure, so that it can be compressed between dam sections and then, as the concrete contracts (thermally or otherwise), the Bondaflex can return to its uncompressed size, continuing to fill the gap between dam sections and providing a level of protection to the dam from seismic events.
Standard Bondaflex products are not adequate for the type of dam construction being used on the Olmstead Dam. Seventy five percent of the shells built require a Bondaflex covering on the Kentucky side of the shell prior to river placement. Since the dam is being constructed from Illinois to Kentucky, the Bondaflex material on the Kentucky side of the shell is exposed to the scouring effects of the Ohio River until the next adjacent shell is placed. Since nature doesn't always cooperate, timing between shell placement could be months or years depending on river elevation. Since the scouring effect from the river is so abrasive, a conventional Bondaflex material would not be able to perform.